Wireless power system with a self-regulating wireless power receiver

ABSTRACT

A method and system for self-regulating wireless power transmitted to a wireless power receiver (WPR) is provided. An auto-tuning network is operably coupled within the WPR. The auto-tuning network comprises an impedance network that dynamically increases, decreases, or maintains amount of the received wirelessly transmitted power by detecting changes in a rectifier load disposed in the WPR and/or in an output voltage of the rectifier in the WPR. The auto-tuning network self-regulates the wireless power received from a wireless power transmitter (WPT) obviating the need for conventional communication messages. The WPT is hence free from a modulator/demodulator block and an out-of-band communication block and can operate over a limited operating range to enable simpler design for passing EMC regulation. Additionally, the WPR implements a receiver-maximum power-signature algorithm for enabling the WPT to detect unsupported receivers, configure its operating point and range, and terminate power transmission when not needed by WPR.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.14/094,750 filed in the United States Patent and Trademark Office onDec. 2, 2013 which claims benefit from U.S. Provisional Application No.61/732,412 filed on Dec. 3, 2012.

BACKGROUND

In wireless power systems, a receiver and a transmitter communicate withone another using a communication protocol. In a conventionalcommunication protocol, the receiver requests the transmitter toincrease, decrease, maintain, stop, etc., the power provided to thereceiver. The communication protocol can be “in band” via for example, aload modulation technique, or be “out of band” such as via Bluetooth® ofBluetooth SIG, Inc., Wi-Fi® of the Wireless Ethernet CompatibilityAlliance, etc.

Conventional communication protocol based power transfer controlinvolves the transmitter changing its frequency across a few hundredkilo hertz (kHz). However, for some applications, it is not desirable tohave a wide range of frequency of operation for wireless power transfer.Also, Federal Communications Commission (FCC) Part 15 Subpart Ccompliance testing becomes difficult because of varying frequency andthe corresponding harmonics.

The conventional communication protocol between the receiver and thetransmitter is also used to send, for example, distress signals, overvoltage conditions, etc. The receiver takes considerable amount of timeto send the message and the transmitter takes considerable amount oftime to decipher the message and react to the sent message, thereforelatency is inherent and there is a time delay. Also, the transmitter maydecipher the message incorrectly, the message may be corrupted, etc.,which could considerably delay the receiver in exiting from an overvoltage condition. The receiver includes additional over voltageprotection (OVP) circuitry that protects the receiver from excessivepower during the time delay. The additional protection circuitry israted to handle a certain amount of power, but if the power exceeds therated power in the protection circuitry, the receiver may be susceptibleto damages. Also while operating, the protection circuitry causes a risein temperature of the receiver which is detrimental to neighboringcomponents, for example, a battery, etc.

Metal object detection is a key safety issue in wireless power delivery.Metal objects, for example, coins, pin-clips, etc., may couple andabsorb some of the magnetic flux emanating from a transmitter whenplaced atop or in close proximity to the transmitter. Because of theeddy currents induced, the metal objects are heated. The heated metalobjects cause damage to the plastic surface of the transmitter or burnskin on contact.

Therefore, there is a long felt but unresolved need for a method andsystem that regulates the amount of wireless power delivered to awireless power receiver without causing any damages to the receiver andthe neighboring components of the receiver. Furthermore, there is a needfor a method and a system that enable a transmitter to detect a metalobject placed atop or in close proximity to the transmitter andterminate transmission of power.

SUMMARY OF THE INVENTION

A method and system for self-regulating a wireless power receiver isprovided. The method and system regulates amount of wireless powerdelivered to the wireless power receiver. The wireless power receiver isconfigured to receive wirelessly transmitted power. An auto-tuningnetwork is operably coupled within the wireless power receiver. Theauto-tuning network is configured to control and regulate the receivedwirelessly transmitted power. The auto-tuning network comprises animpedance network dynamically configured to increase, decrease, ormaintain amount of the received wirelessly transmitted power. Theimpedance network comprises one or more of passive electroniccomponents, active electronic components, and electronic switches. Theauto-tuning network is configured to detect changes in one or more of aload of a rectifier operably disposed in the self-regulating wirelesspower receiver, and in an output voltage of the rectifier, and tocounteract the detected changes if the changes exceed a safe operatingrange.

The wireless power receiver, via the auto-tuning network, self-regulatesto draw the required amount of power from a wireless power transmitter.In a sudden over voltage condition, for example, on account of a loadtransient, the auto-tuning network detects the over voltage and performsquick remedial action. The auto-tuning network provides effective andfaster over voltage protection (OVP) than possible with a scheme thatrelies on communicating with the wireless power transmitter. The needfor a conventional communication protocol from the wireless powerreceiver to the wireless power transmitter is obviated since thefunctions that require the communication protocol to exist are handledby the auto-tuning network with significantly faster response times.

The method and system disclosed herein also simplifies the wirelesspower transmitter design. The wireless power transmitter does not need aconventional modulator/demodulator block and an out-of-bandcommunication block typically contained in the wireless powertransmitter for processing messages from and communicating messages tothe wireless power receiver. The wireless power receiver, via theauto-tuning network, receives the required amount of wirelesslytransmitted power from the wireless power transmitter withoutcommunicating messages to the wireless power transmitter. As a result, afew of the wireless protocol communication function blocks, such as themodulator/demodulator block and the out-of-band communication block thatare typically contained in the wireless power transmitter can beeliminated. The modulator/demodulator block and the out-of-bandcommunication block are built with many passive components, activecomponents, switches and firmware resources. Therefore, elimination ofthe modulator/demodulator block and the out-of-band communication blocksimplifies and substantially reduces the cost of the wireless powertransmitter design. Also, the wireless power transmitter can operate ata fixed operating point, for example, a frequency, a duty cycle etc., orwithin a narrow range and/or a set of operating points. Such animplementation, will allow the wireless power transmitter to passelectromagnetic compliance (EMC) regulation easily.

In an embodiment, to avoid a heated metal object safety issue caused byeddy currents induced when metal objects are placed atop or in closeproximity to the transmitter, the method and the system disclosed hereinimplements a receiver-maximum power-signature algorithm that enables thewireless power transmitter to detect metal objects and unsupportedreceivers and terminate transmission of power. The wireless powertransmitter is aware of the maximum power needs of the wireless powerreceiver via the receiver-maximum power-signature algorithm. Thewireless power transmitter configures its circuitry, input voltage,operating point, etc., to deliver no more than the required level ofmaximum power to the wireless power receiver. Via the receiver-maximumpower-signature algorithm, the wireless power transmitter alsoterminates transmission of wireless power when the wireless powerreceiver does not need any further power or if the wireless powerreceiver is removed, thereby increasing the overall efficiency ofwireless power delivery.

By incorporating the self-regulating wireless power receiver, thereceiver-maximum power-signature algorithm and the simplified, limitedoperating point wireless power transmitter, the method and systemdisclosed herein allows building of a wireless power system thatprovides wireless power to an electronic device without the need for aconventional communication protocol between the wireless powertransmitter and the wireless power receiver.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 exemplarily illustrates a schematic diagram of a wireless powersystem comprising a wireless power transmitter and a self-regulatingwireless power receiver.

FIG. 1A exemplarily illustrates the first embodiment of the auto-tuningnetwork in a self-regulating wireless power receiver.

FIG. 1B exemplarily illustrates the second embodiment of the auto-tuningnetwork in a self-regulating wireless power receiver.

FIG. 1C exemplarily illustrates the third embodiment of the auto-tuningnetwork in a self-regulating wireless power receiver.

FIG. 1D exemplarily illustrates the fourth embodiment of the auto-tuningnetwork in a self-regulating wireless power receiver.

FIG. 2 exemplarily illustrates a schematic diagram of a wireless powertransmitter free from a modulator/demodulator block and an out-of-bandcommunication block.

FIG. 3 exemplarily illustrates a flow chart comprising the steps forestablishing a stable and optimal power transfer from the wireless powertransmitter to the wireless power receiver.

FIG. 4 exemplarily illustrates a schematic diagram of a wireless powersystem comprising a wireless power transmitter and a self-regulatingwireless power receiver that includes a reconfigurable rectifier.

FIG. 5A exemplarily illustrates the first embodiment of thereconfigurable rectifier in a self-regulating wireless power receiver.

FIG. 5B exemplarily illustrates the second embodiment of thereconfigurable rectifier in a self-regulating wireless power receiver.

FIG. 5C exemplarily illustrates the third embodiment of thereconfigurable rectifier in a self-regulating wireless power receiver.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 exemplarily illustrates a schematic diagram of a wireless powersystem 100 comprising a wireless power transmitter 100 a and aself-regulating wireless power receiver 100 b. The wireless powerreceiver 100 b of the wireless power system 100 employs an auto-tuningscheme to control the amount of power that the wireless power receiver100 b receives. A switch network 101 is configured to receive an inputpower and an input voltage. An impedance network 102 is connectedbetween the switch network 101 and a transmitter coil 103. The inputpower wirelessly transmitted to the wireless power receiver 100 b ismagnetic field based using inductive coupling. The transmitter coil 103is used for inducing a magnetic field to a coupling region for providingenergy transfer to the wireless power receiver 100 b. The wireless powertransmitter 100 a transmits input power to the wireless power receiver100 b by emanating the magnetic field using the transmitter coil 103.The wireless power receiver 100 b comprises a receiver coil 104 thatpicks up the magnetic field with a certain coupling coefficient thatexists between the transmitter coil 103 and the receiver coil 104, anauto-tuning network 105 that regulates power received by the wirelesspower receiver 100 b, and a rectifier 106 that rectifies the alternatingcurrent (AC) to obtain direct current (DC). A capacitor 107 in thewireless power receiver 100 b filters stray AC components. A pure DCoutput is received across a rectifier load 108.

The auto-tuning network 105 controls and regulates the wireless inputpower received by the wireless power receiver 100 b. The auto-tuningnetwork 105 in the wireless power receiver 100 b controls powertransfer, protects against over voltage, and provides improved loadtransient response. The auto-tuning network 105 comprises an impedancenetwork that is dynamically tuned to increase, decrease, or maintain theamount of wireless input power received by the wireless power receiver100 b. The impedance network comprises a combination of passivecomponents such as inductors, capacitors, resistors, etc., activecomponents such as metal oxide semiconductor field effect transistors(MOSFETs), bipolars, operational amplifiers, Analog to Digital Converter(ADC), Micro-controllers (MCU) etc., and switches.

The auto-tuning network 105 regulates the output voltage “Vrect” of therectifier 106 across the rectifier load 108 that can swinginstantaneously and exceed recommended limits when the load across therectifier 106 changes. By performing this action, the auto-tuningnetwork 105 protects the wireless power receiver 100 b from an unsafecondition. The auto-tuning network 105 senses the changes in therectifier load 108 and/or the output voltage Vrect of the rectifier 106and quickly counteracts the changes if the changes exceed a safeoperating range. For example, the auto-tuning network 105 rapidly tunesto increase the wireless input power at the wireless power receiver 100b when the rectifier 106 output voltage Vrect drops below the safeoperating range. In another example, the auto-tuning network 105 rapidlytunes to decrease the wireless input power at the wireless powerreceiver 100 b when the rectifier 106 output voltage Vrect increasesabove the safe operating range. The output voltage Vrect of therectifier 106 is therefore maintained within a safe range without theneed for a more elaborate over voltage protection (OVP) scheme. Changesin the auto-tuning network 105 affect the reflected impedance seen bythe wireless power transmitter 100 a. This alters the wireless powertransmitted by the wireless power transmitter 100 a to the wirelesspower receiver 100 b.

FIG. 1A exemplarily illustrates the first embodiment of the auto-tuningnetwork 105 of the self-regulating wireless power receiver 100 b. Inthis embodiment, the auto-tuning network 105 includes a Vrect SensingBlock 109, a Power Tuning Block 110, a series resonant capacitor Cs anda parallel switch-capacitor network consisting of “n” parallelcapacitors C1, C2, . . . Cn and “n” switches S1, S2, . . . Sn. In thisembodiment, the parallel switch-capacitor network is connected acrossthe 2 alternating current (AC) IOs of the rectifier 106. The VrectSensing Block 109 measures the rectifier 106 output voltage Vrectconstantly or periodically. The Power Tuning Block 110 compares themeasured voltage Vrect with its configured threshold levels. Based onthe comparison, the Power Tuning Block 110 activates switches S1, S2, .. . Sn. The switches may be turned on or turned off or may be pulsed onand off at a certain frequency and duty cycle. When a switch S1, S2, . .. Sn is turned on, the associated capacitor C1, C2, . . . Cn on the sameleg is activated and impacts the reflected impedance of the wirelesspower receiver and hence the amount of wireless power received. TheVrect Sensing Block 109 senses the changes in the rectifier 106 outputvoltage Vrect and the Power Tuning Block 110 quickly counteracts thechanges if the changes exceed a safe operating range. For example, ifthe rectifier 106 output voltage Vrect drops below the safe operatingrange, the Power Tuning Block 110 turns on switches S1 and S2 toincrease the amount of wireless power received. The Power Tuning Block110 progressively turns on more switches until wireless power receivedrestores the output voltage Vrect of the rectifier to the safe operatingrange. In another example, if the rectifier 106 output voltage Vrectincreases above the safe operating range, the Power Tuning Block 110progressively decreases the on-time duty cycle of switches S1, S2, . . .Sn, to decreases the level of wireless power received until Vrect isrestored to the safe operating range. As an additional embodiment, theresonant series capacitor Cs may not be present and the coil 104 isconnected directly to the parallel switch-capacitor network.

FIG. 1B exemplarily illustrates the second embodiment of the auto-tuningnetwork 105 of the self-regulating wireless power receiver 100 b. Inthis embodiment, the auto-tuning network 105 includes a Vrect SensingBlock 109, a Power Tuning Block 110, a series resonant capacitor Cs, aparallel resonant capacitor Cd and a parallel switch-capacitor networkconsisting of “n” parallel capacitors C1, C2, . . . Cn and “n” switchesS1, S2, . . . Sn. In this embodiment, the parallel switch-capacitornetwork is connected asymmetrically between one of the alternatingcurrent (AC) IOs of the rectifier 106 and ground. The Vrect SensingBlock 109 measures the rectifier 106 output voltage Vrect constantly orperiodically. The Power Tuning Block 110 compares the measured voltageVrect with its configured threshold levels. Based on the comparison, thePower Tuning Block 110 activates switches S1, S2, . . . Sn. The switchesmay be turned on or turned off or may be pulsed on and off at a certainfrequency and duty cycle. When a switch S1, S2, . . . Sn is turned on,the associated capacitor C1, C2, . . . Cn on the same leg is activatedand impacts the reflected impedance of the wireless power receiver andhence the amount of wireless power received. The Vrect Sensing Block 109senses the changes in the rectifier 106 output voltage Vrect and thePower Tuning Block 110 quickly counteracts the changes if the changesexceed a safe operating range. For example, if the rectifier 106 outputvoltage Vrect drops below the safe operating range, the Power TuningBlock 110 turns on switches S1 and S2 to increase the amount of wirelesspower received. The Power Tuning Block 110 progressively turns on moreswitches until wireless power received restores the output voltage Vrectof the rectifier to the safe operating range. In another example, if therectifier 106 output voltage Vrect increases above the safe operatingrange, the Power Tuning Block 110 progressively decreases the on-timeduty cycle of switches S1, S2, . . . Sn, to decreases the level ofwireless power received until Vrect is restored to the safe operatingrange. As an additional embodiment, the resonant series capacitor Cs maynot be present and the coil 104 is connected directly across Cd.

FIG. 1C exemplarily illustrates the third embodiment of the auto-tuningnetwork 105 of the self-regulating wireless power receiver 100 b. Inthis embodiment, the auto-tuning network 105 includes a Vrect SensingBlock 109, a Power Tuning Block 110, a series resonant capacitor Cs, aparallel resonant capacitor Cd, a first parallel switch-capacitornetwork consisting of “n” parallel capacitors C1, C2, . . . Cn and “n”switches S1, S2, . . . Sn and a second parallel switch-capacitor networkconsisting of “n” parallel capacitors D1, D2, . . . Dn and “n” switchesE1, E2, . . . En. In this embodiment, the two parallel switch-capacitornetworks in combination together are connected symmetrically betweenboth the alternating current (AC) IOs of the rectifier 106 and ground.The Vrect Sensing Block 109 measures the rectifier 106 output voltageVrect constantly or periodically. The Power Tuning Block 110 comparesthe measured voltage Vrect with its configured threshold levels. Basedon the comparison, the Power Tuning Block 110 activates switches S1, S2,. . . Sn and switches E1, E2, . . . En. The switches may be turned on orturned off or may be pulsed on and off at a certain frequency and dutycycle. When a switch, for example, S1, is turned on, the associatedcapacitor, for example C1, on the same leg is activated and impacts thereflected impedance of the wireless power receiver and hence the amountof wireless power received. The Vrect Sensing Block 109 senses thechanges in the rectifier 106 output voltage Vrect and the Power TuningBlock 110 quickly counteracts the changes if the changes exceed a safeoperating range. For example, if the rectifier 106 output voltage Vrectdrops below the safe operating range, the Power Tuning Block 110 turnson switches S1 and E1 to increase the amount of wireless power received.The Power Tuning Block 110 progressively turns on more switchessymmetrically until wireless power received restores the output voltageVrect of the rectifier to the safe operating range. In another example,if the rectifier 106 output voltage Vrect increases above the safeoperating range, the Power Tuning Block 110 progressively decreases theon-time duty cycle of switches S1, E1 to decreases the level of wirelesspower received until Vrect is restored to the safe operating range. Asan additional embodiment, the resonant series capacitor Cs may not bepresent and the coil 104 is connected directly across Cd.

FIG. 1D exemplarily illustrates the fourth embodiment of the auto-tuningnetwork 105 of the self-regulating wireless power receiver 100 b. Inthis embodiment, the auto-tuning network 105 includes a Vrect SensingBlock 109, a Power Tuning Block 110, a paralled resonant capacitor Cdand a parallel switch-capacitor network consisting of “n” parallelcapacitors C1, C2, . . . Cn and “n” switches S1, S2, . . . Sn. In thisembodiment, the parallel switch-capacitor network is connected betweenthe coil 104 and one of the alternating current (AC) IOs of therectifier 106. The Vrect Sensing Block 109 measures the rectifier 106output voltage Vrect constantly or periodically. The Power Tuning Block110 compares the measured voltage Vrect with its configured thresholdlevels. Based on the comparison, the Power Tuning Block 110 activatesswitches S1, S2, . . . Sn. The switches may be turned on or turned offor may be pulsed on and off at a certain frequency and duty cycle. Whena switch S1, S2, . . . Sn is turned on, the associated capacitor C1, C2,. . . Cn on the same leg is activated and impacts the reflectedimpedance of the wireless power receiver and hence the amount ofwireless power received. The Vrect Sensing Block 109 senses the changesin the rectifier 106 output voltage Vrect and the Power Tuning Block 110quickly counteracts the changes if the changes exceed a safe operatingrange. For example, if the rectifier 106 output voltage Vrect dropsbelow the safe operating range, the Power Tuning Block 110 turns onswitches S1 and S2 to increase the amount of wireless power received.The Power Tuning Block 110 progressively turns on more switches untilwireless power received restores the output voltage Vrect of therectifier to the safe operating range. In another example, if therectifier 106 output voltage Vrect increases above the safe operatingrange, the Power Tuning Block 110 progressively decreases the on-timeduty cycle of switches S1, S2, . . . Sn, to decreases the level ofwireless power received until Vrect is restored to the safe operatingrange. As an additional embodiment, the resonant parallel capacitor Cdmay not be present in certain applications.

FIG. 2 exemplarily illustrates a schematic diagram of a wireless powertransmitter 100 a without a modulator/demodulator block and anout-of-band communication block. The wireless power transmitter 100 adisclosed herein comprises a switch network 101 configured to receive aninput voltage and an input current from a voltage source. The wirelesspower transmitter 100 a further comprises an impedance network 102represented as a Zmatch block connected between the switch network 101and a transmitter coil 103. The impedance network 102 comprises one ormore of passive electronic components, for example, a resistor, acapacitor, a magnetic device, a transducer, etc., active electroniccomponents, for example, a diode, a transistor such as a metal oxidesemiconductor field effect transistor (MOSFET), a bipolar transistor,operational amplifiers, an optoelectronic device, etc.; and electronicswitches. The wireless power transmitter 100 a further comprises ananalog to digital converter (ADC) 202, where the ADC 202 is operablycoupled to a control logic circuit 201 of the wireless power transmitter100 a. The ADC 202 measures various parameters such as the input voltageVin, the input current Iin, the transmitter coil 103 voltage VCoil, thetransmitter coil 103 temperature, the transmitter coil 103 currentICoil, etc., and feeds such information in realtime to the control logiccircuit 201. The control logic circuit 201 processes all the collectedrealtime information via its control circuits, state machines,algorithms, firmware, etc., and in turn outputs a pulse width modulation(PWM) signal to the switch network 101.

The wireless power transmitter 100 a scans and detects the presence of awireless power receiver 100 b, exemplarily illustrated in FIG. 1, in itsvicinity. On detecting the presence of the wireless power receiver 100b, the wireless power transmitter 100 a configures the switch network101 and tunes the impedance network 102 to create sufficient fieldlinkage, for example, a magnetic flux field linkage to transmit powerwirelessly to the wireless power receiver 100 b. In the wireless powersystem 100 disclosed herein, the wireless power transmitter 100 a doesnot contain a conventional modulator/demodulator block which istypically needed for processing in-band messages from and communicatingin-band messages to the wireless power receiver 100 b in a wirelesspower protocol of the wireless power receiver 100 b. The wireless powertransmitter 100 a disclosed herein also does not contain a conventionalout-of-band communication block which is also typically used forprocessing out-of-band messages from and communicating out-of-bandmessages to the wireless power receiver 100 b in a wireless powerprotocol of the wireless power receiver 100 b.

The wireless power receiver 100 b, using the auto-tuning network 105exemplarily illustrated in FIG. 1 and FIGS. 1A-1D is configured tosafely receive the wirelessly transmitted power from the wireless powertransmitter 100 a via the self regulatory auto-tuning network 105. Thewireless power receiver 100 b, via the auto-tuning network 105, receivesthe required amount of wirelessly transmitted power from the wirelesspower transmitter 100 a without communicating conventional messages suchas increase power, decrease power, maintain power, stop power, etc., tothe wireless power transmitter 100 a. The need for such conventionalcommunication messages from the wireless power receiver 100 b to thewireless power transmitter 100 a is obviated since the end resulttargeted by those communication messages is achieved by the auto-tuningnetwork 105 with substantially faster response times. The elimination ofsuch conventional communication messages enables simplification of thedesign of the wireless power transmitter 100 a and the wireless powerreceiver 100 b by elimination of circuitry (modulator/demodulator blockand an out-of-band communication block) and firmware to processes,error-correct, decipher and respond to those messages. Because of such asimplification, the wireless power system 100 can be built at lower costand smaller size and can operate at higher efficiency. Also, because ofthe auto-tuning network 105 operably coupled within the self-regulatingwireless power receiver 100 b, the wireless power transmitter 100 a canoperate at a fixed operating point, for example, at a fixed frequencyand duty cycle or within a narrow range and/or set of operating pointswhich enables the wireless power transmitter 100 a to implement and passelectromagnetic compliance (EMC) regulation more easily.

When metal objects are placed atop or in close proximity of the wirelesspower transmitter 100 a, eddy currents are induced in the metal objectas a result of the magnetic field emanating from the wireless powertransmitter 100 a. When the metal object has low resistivity, these eddycurrents cause the metal object to heat up leading to a safety issue.The wireless power transmitter 100 a has various algorithms fordetecting metal objects and turning off power to eliminate this heatedmetal object safety issue. In addition, the wireless power transmitter100 a turns on substantial power delivery only when it senses a goodwireless power receiver 100 b. This enables low standby powerconsumption at the wireless power transmitter 100 a when there is notany good wireless power receiver 100 b in the wireless powertransmitter's vicinity. Additionally, the wireless power transmitter 100a ensures that a careful level of power is delivered to the wirelesspower receiver 100 b without compromising required performance andwithout overwhelming and damaging the wireless power receiver 100 b withtoo much power. In an embodiment, so as to avoid hot metal objects, tohave low standby power and to have safe power delivery to the wirelesspower receiver, the method and the system 100 disclosed hereinimplements a receiver-maximum-power-signature algorithm. This algorithmenables the wireless power transmitter 100 a to detect metal objects andterminate transmission of power. This algorithm enables the wirelesspower transmitter 100 a to detect the presence of a good wireless powerreceiver 100 b and then start providing substantial power. Via thisalgorithm, the wireless power transmitter 100 a is also aware of themaximum power needs of the wireless power receiver 100 b. The wirelesspower transmitter 100 a then configures its operating point to deliverthe required level of maximum power. Via thereceiver-maximum-power-signature algorithm, the wireless powertransmitter 100 a can also terminate transmission of wireless power whenthe wireless power receiver 100 b does not need any further power,thereby increasing the overall efficiency of wireless power delivery.

FIG. 3 exemplarily illustrates a flow chart comprising the steps forestablishing a stable and optimal power transfer from the wireless powertransmitter 100 a to the wireless power receiver 100 b via thereceiver-maximum-power-signature algorithm. On reset, the process beginswith the wireless power transmitter 100 a transmitting 301 a short burstof wireless power to detect 302 the presence of a wireless powerreceiver 100 b in its vicinity. If a wireless power receiver 100 b isnot detected, the wireless power transmitter 100 a shuts down 303 into adeep sleep after programming a timer to restore the wireless powertransmitter 100 a back to its normal operating mode after “T1” seconds.If a wireless power receiver 100 b is detected, the wireless powertransmitter 100 a transmits 304 a minimum amount of power to thewireless power receiver 100 b for a fixed time interval.

On receiving initial power from the wireless power transmitter 100 a,the self-regulating wireless power receiver 100 b initiatesimplementation of the receiver-maximum-power-signature algorithm. Thereceiver-maximum-power-signature algorithm defines instructions forvarying, that is, increasing and decreasing the input impedance of thewireless power receiver 100 b by a specified amount for predeterminedintervals of time. For example, as per thereceiver-maximum-power-signature algorithm, the self-regulating wirelesspower receiver 100 b may increase its input impedance by about 10% for 5milliseconds and then reduce its input impedance by about 10% for 5milliseconds and may repeat this pattern about 10 times for a total timeperiod of 100 milliseconds. The input impedance of the wireless powerreceiver 100 b is the impedance of the wireless power receiver whenlooking into the wireless power receiver from the receiving coil 104.The input impedance of the wireless power receiver 100 b is varied byvarying its real and/or reactive parts. The reactive part of the inputimpedance of the wireless power receiver 100 b is varied via changes inthe auto-tuning network 105 of the wireless power receiver 100 b asexemplarily illustrated in FIGS. 1A-1D and described previously. Thereal part of the input impedance of the wireless power receiver 100 b isvaried by adding and removing resistive loads in parallel with theactual load 108. As a result of the changes in the input impedance ofthe wireless power receiver 100 b, the reflected impedance as seen bythe wireless power transmitter 100 a is consequently increased ordecreased. The receiver-maximum-power-signature algorithm controls thepattern of input impedance change and via these impedance changes, thewireless power receiver 100 b conveys its maximum-power-signature to thewireless power transmitter 100 a.

On detecting a wireless power receiver 100 b, the wireless powertransmitter 100 a provides initial power to the wireless power receiver100 b for a fixed amount of time, for example, 100 milliseconds. Whileproviding initial power, the wireless power transmitter 100 a tracksparameters such as transmitter coil voltage VCoil, transmitter coilcurrent ICoil, etc., to observe changes in the reflected impedancecaused as a result of changes in the input impedance of the wirelesspower receiver 100 b. The reflected impedance changes may also beobserved by tracking the voltage and/or current flowing in the switchnetwork 101 or other parts of the wireless power transmitter 100 a. Viatracking parameters that are dependent on the reflected impedance, thewireless power transmitter 100 a can determine 305 whether the wirelesspower receiver 100 b is a metal object. When the reflected impedancechanges follows one of the predefined receiver-maximum-power-signaturesfor a pre-determined fraction of the initial power time period, forexample, say 50% of the initial power time period which would be 50milliseconds, the wireless power transmitter 100 a recognizes that thewireless power transmitter 100 a is transmitting power to a safenon-metal object wireless power receiver 100 b and hence, continues toprovide 307 power.

While providing power, the wireless power transmitter 100 a receives thecomplete receiver-maximum-power-signature from the wireless powerreceiver 100 b. The wireless power transmitter 100 a decodes anddetermines the maximum power level of the receiver from that signature.Based on the determined maximum power level, the wireless powertransmitter 100 a selects and set its operating point and operatingrange by configuring its switch network 101, the impedance network 102,and the transmitter coil 103 to be able to deliver that maximum amountof power. For example, if the received maximum-power-signature is“10101010101010101010”, the wireless power transmitter 100 a determinesthe maximum power level to be 10 Watts and configures its operatingfrequency to (say) 130 khz and its duty cycle to not exceed 40% so as todeliver a maximum of 10 W to the wireless power receiver. Additionally,based on the strength of the reflected impedance changes, the wirelesspower transmitter 100 a senses the level of magnetic field flux linkagecoupling between the wireless power transmitter 100 a and the wirelesspower receiver 100 b. The wireless power transmitter 100 a considers thesensed level of coupling when selecting and setting its operating pointand range. For example, when the level of coupling is strong, to delivera maximum power of 10 Watts, the wireless power transmitter 100 a mayconfigure itself to operate at a fixed frequency of 130 khz and a dutycycle not to exceed 40%. When the level of coupling is weak, to delivera maximum power of 10 Watts, the wireless power transmitter 100 a mayconfigure itself to operate at a fixed frequency of 128 khz and allow aduty cycle of up to 50%.

When the reflected impedance changes does not follow any of thepredefined receiver-maximum-power-signatures for the predeterminedfraction of the initial power time period, the wireless powertransmitter 100 a recognizes the presence of an unsupported object,potentially, an unsafe, metal object and hence, terminates further powertransmission. That is, if the wireless power receiver 100 b is a metalobject or some unknown object, the wireless power transmitter 100 ashuts down 306 into a deep sleep after programming a timer to restorethe wireless power transmitter 100 a back to its normal operating modeafter “T2” seconds.

The input impedance of a metal object does not vary in sync with thepredefined receiver-maximum-power-signature patterns, thereby virtuallyguaranteeing that the wireless power transmitter 100 a will not falselyrecognize a metal object as a good wireless power receiver 100 b. As perthe receiver-maximum-power-signature algorithm, the wireless powerreceiver 100 b modulates its input impedance as per its maximum powersignature periodically, for example, every 0.5 seconds. For the purposeof the receiver-maximum-power-signature algorithm, the wireless powerreceiver 100 b carefully adopts only those input impedance changes whichpreserve the rectifier output voltage Vrect in the safe operating range.

The wireless power transmitter 100 a checks 308 whether the wirelesspower receiver 100 b is sending the maximum power signatureperiodically. The wireless power transmitter 100 a continues to providepower as long as the wireless power transmitter 100 a receives themaximum power signature periodically, for example, at least onesignature every 2 seconds. If the maximum power signature is received,the wireless power transmitter 100 a continues to provide 307 power andre-configures its operating point and range if required. If the maximumpower signature is not received as per its periodic rate, the wirelesspower transmitter 100 a assumes that the wireless power receiver 100 bhas been removed or does not require further power. Hence, the wirelesspower transmitter 100 a terminates transmitting power and shuts down 309into a deep sleep after programming a timer to restore the wirelesspower transmitter 100 a back to its normal operating mode after “T3”seconds.

While providing initial power, the wireless power transmitter 100 atracks parameters such as transmitter coil voltage VCoil, transmittercoil current ICoil, etc., to observe changes in the reflected impedancecaused as a result of changes in the input impedance of the wirelesspower receiver 100 b. In an embodiment, the wireless power transmitter100 a employs a simple peak detector mechanism to extract the envelopeof the voltage and/or current that is in the coil or switch network orother parts of the wireless power transmitter 100 a. Embedded in theenvelope of the voltage and/or current is thereceiver-maximum-power-signature. Via its analog to digital converter(ADC) 202 exemplarily illustrated in FIG. 2, the wireless powertransmitter 100 a is aware of the extracted envelope of the voltageand/or current and hence, the receiver's maximum power signature. Viaits ADC 202, the wireless power transmitter 100 a is also aware of thestrength of the reflected impedance changes. The wireless powertransmitter 100 a uses this information to estimate the level ofcoupling between the wireless power transmitter 100 a and the wirelesspower receiver 100 b. In a second embodiment, the wireless powertransmitter 100 a employs a simple zero crossing detector mechanism toextract the phase difference between the voltage and current that is inthe coil or switch network or other parts of the wireless powertransmitter 100 a. Embedded in the phase difference between the voltageand current is the receiver-maximum-power-signature. The wireless powertransmitter 100 a observes the variations in the phase difference toextract the receiver-maximum-power-signature. The wireless powertransmitter 100 a also observes the magnitude of these phase differencevariations. The wireless power transmitter 100 a uses this magnitudeinformation to estimate the level of coupling between the wireless powertransmitter 100 a and the wireless power receiver 100 b.

By incorporating the self-regulating wireless power receiver 100 b, thereceiver-maximum power-signature algorithm and the simplified, limitedoperating point wireless power transmitter 100 a, the method and system100 disclosed herein allows building of a wireless power system thatprovides stable, safe and efficient wireless power to an electronicdevice without the need for a conventional communication protocolmessages between the wireless power transmitter 100 a and the wirelesspower receiver 100 b.

FIG. 4 exemplarily illustrates a schematic diagram of a wireless powersystem 400 comprising a wireless power transmitter 400 a and aself-regulating wireless power receiver 400 b. The wireless powerreceiver 400 b of the wireless power system 400 employs a dynamicallyreconfigurable scheme to control the amount of power that the wirelesspower receiver 400 b delivers to its load 408. The wireless powertransmitter 400 a of the wireless power system 400 includes a switchnetwork 401 that is configured to receive an input power at an inputvoltage ‘Vin’. An impedance network 402 is connected between the switchnetwork 401 and a transmitter coil 403. The transmitter coil 403 ofwireless power transmitter 400 a is used for creating a magnetic fieldto a coupling region for providing energy transfer to the wireless powerreceiver 400 b. The wireless power transmitter 400 a transmits powerfrom its input to the wireless power receiver 400 b by emanating amagnetic field from the transmitter coil 403. Power is wirelesslyreceived by the wireless power receiver 400 b via one of a magneticfield, an electric field, an electromagnetic field or a combinationthereof. FIG. 4 exemplarily illustrates wireless power transfer via amagnetic field using inductive coupling. The receiver coil 404 of thewireless power receiver 400 b intersects and converts this magneticfield into alternating current (AC) power. In inductive coupling, theamount of AC power picked up is influenced by the coupling coefficient‘k’ that exists between the transmitter coil 403 and the receiver coil404. In addition, the AC power picked up is influenced by the impedancenetwork 405, the rectifier 406 and the load 408 of the wireless powerreceiver 400 b. The AC power flows from the receiver coil 404 to therectifier 406 via the impedance network 405. In the invention disclosedherein, the rectifier 406 of the wireless power receiver 400 b is adynamically reconfigurable rectifier. Besides rectifying the alternatingcurrent (AC) power into direct current (DC) power, the rectifier 406also reconfigures its mode of operation dynamically to regulate theamount of power delivered to its load 408. A capacitor 407 in thewireless power receiver 400 b filters stray AC components and a steadyDC power is delivered to the load 408. In an embodiment, additionalpower regulation circuitry such as Low Voltage Dropout (LDO) regulator,buck circuitry, buck-boost circuitry, Zener diode, etc., may be includedto further reduce the voltage ripple and/or transients on the powerdelivered to the load 408.

The reconfigurable rectifier 406 controls and regulates the powerdelivered by the wireless power receiver 400 b to its load 408. Thereconfigurable rectifier 406 in the wireless power receiver 400 bcontrols power transfer, protects against over voltage, and providesimproved load transient response. The reconfigurable rectifier 406comprises an intelligent switch network that is dynamically reconfiguredto increase, decrease, or maintain the amount of wireless input powerreceived and/or delivered to the load 408 by the wireless power receiver400 b. The intelligent switch network comprises a combination of passivecomponents such as capacitors, diodes, schottky diodes, etc., and activecomponents such as metal oxide semiconductor field effect transistors(MOSFETs), bipolars, operational amplifiers, comparators, Analog toDigital Converter (ADC), Micro-controllers (MCU) etc., and switches.

The reconfigurable rectifier 406 regulates the voltage “Vrect” acrossthe load 408. Vrect can swing instantaneously and exceed recommendedlimits under varied circumstances such as when the load 408 changes orwhen the amount of flux density/wireless power provided by the wirelesspower transmitter 400 a changes or when the coupling coefficient ‘k’changes, etc. By detecting and rapidly reconfiguring itself, thereconfigurable rectifier 406 protects the wireless power receiver 400 bfrom an unsafe condition. The intelligent reconfigurable rectifier 406senses the changes in the load 408 and/or the voltage Vrect and quicklycounteracts the changes if the changes exceed a safe operating range.For example, the rectifier 406 rapidly switches from a Half-Bridge (HB)rectification topology to a Full-Bridge (FB) rectification topology toincrease the power delivered to the load 408 when Vrect drops below thesafe operating range at the wireless power receiver 400 b. In anotherexample, the rectifier 406 rapidly switches from a Full-Bridge (FB)rectification topology to a bypass topology to decrease the powerdelivered to the load 408 when Vrect increases above the safe operatingrange at the wireless power receiver 400 b. The voltage Vrect istherefore maintained within a safe range without the need for a moreelaborate over voltage protection (OVP) scheme. Changes in the rectifier406 configuration may affect the reflected impedance seen by thewireless power transmitter 400 a. This may additionally alter thewireless power transmitted by the wireless power transmitter 400 a tothe wireless power receiver 400 b and hence further counteract thetransient.

FIG. 5A exemplarily illustrates the first embodiment of the intelligentreconfigurable rectifier 406 of the self-regulating wireless powerreceiver 400 b. In this embodiment, the rectifier 406 includes a VrectSensing Block 409, a Power Tuning Block 410 and switches S1, S2, S3 andS4. The Vrect Sensing Block 409 measures the voltage Vrect constantly orperiodically. The Power Tuning Block 410 compares the measured voltageVrect with its configured threshold levels. Based on the comparison, thePower Tuning Block 410 activates switches S1, S2, S3 and S4. Theswitches may be turned on or turned off or may be pulsed on and off at acertain frequency and duty cycle. The switches are also activated incertain combinations to achieve the desired power delivery and controlof Vrect. For example, to bypass the power delivery entirely to theload, the Power Tuning Block 410 turns on switches S2 and S4 together.In such a case, the rectifier 406 returns all the received AC power backto the receiver coil 403 and no power is delivered to the load 408.Alternately, the Power Tuning Block 410 may activate and deactivate S2and S4 simultaneously at a certain frequency and duty cycle to maintainVrect and power delivery to load 408 at a desired level. The PowerTuning Block 410 may configure the switches into Half-Bridge (HB) orFull-Bridge (FB) mode of operation and may select between thesedifferent modes dynamically to counteract unsafe changes on Vrect. Forexample, if voltage Vrect drops below the safe operating range, thePower Tuning Block 410 configures the switches S1, S2, S3 and S4 in HBmode to increase the amount of power delivered to the load 408. ThePower Tuning Block 410 may progressively reconfigure the switches intoFB mode to further increase the power until Vrect is restored into thesafe operating range. In another example, when Vrect increases rapidlyabove the recommended high threshold, the Power Tuning Block 410 mayswitch from a 100% FB configuration to a combination of FB and bypassrectifier configuration at a 50% duty cycle each.

FIG. 5B exemplarily illustrates the second embodiment of the intelligentreconfigurable rectifier 406 of the self-regulating wireless powerreceiver 400 b. In this embodiment, the rectifier 406 includes a VrectSensing Block 409, a Power Tuning Block 410, diodes D1 and D2,capacitors C1 and C2 and switch S1. The Vrect Sensing Block 409 measuresthe voltage Vrect constantly or periodically. The Power Tuning Block 410compares the measured voltage Vrect with its configured thresholdlevels. Based on the comparison, the Power Tuning Block 410 activatesswitch S1. The switch S1 may be turned on or turned off or may be pulsedon and off at a certain frequency and duty cycle to achieve the desiredpower delivery and control of Vrect. For example, to reduce the powerdelivery to the load, the Power Tuning Block 410 turns off switch S1.Alternately, to partially reduce power delivery to load 408 and reduceVrect, the Power Tuning Block 410 may activate and deactivate S1 at acertain frequency and duty cycle. If more power is required by the load,the Power Tuning Block 410 may activate S1 at full 100% duty cycle. Whenswitch S1 is activated, the power is rectified in Voltage-Doubler (VD)Mode while when switch S1 is deactivated, the power is rectified inHalf-Bridge (HB) mode of operation and selection between these modesdynamically enables the rectifier 406 to counteract unsafe changes onVrect. For example, if voltage Vrect drops below the safe operatingrange, the Power Tuning Block 410 activates switch S1 at a certainfrequency and duty cycle to increase the amount of power delivered tothe load 408. In another example, when Vrect increases rapidly above therecommended high threshold, the Power Tuning Block 410 may deactivateswitch S1 entirely.

FIG. 5C exemplarily illustrates the third embodiment of the intelligentreconfigurable rectifier 406 of the self-regulating wireless powerreceiver 400 b. In this embodiment, the rectifier 406 includes a VrectSensing Block 409, a Power Tuning Block 410, diodes D1, D2 and D3,capacitors C1 and C2 and switches S1 and S2. The Vrect Sensing Block 409measures the voltage Vrect constantly or periodically. The Power TuningBlock 410 compares the measured voltage Vrect with its configuredthreshold levels. Based on the comparison, the Power Tuning Block 410activates switches S1 and S2. The switches S1 and S2 may be turned on orturned off or may be pulsed on and off at a certain frequency and dutycycle to achieve the desired power delivery and control of Vrect. Forexample, to reduce the power delivery to the load, the Power TuningBlock 410 turns off switches S1 and S2. Alternately, to partially reducepower delivery to load 408 and reduce Vrect, the Power Tuning Block 410may activate and deactivate S1 and S2 at a certain frequency and dutycycle. If more power is required by the load, the Power Tuning Block 410may activate S1 and S2 at full 100% duty cycle. When both switch S1 andS2 are activated, the power is rectified in Voltage-Tripler (VD) modewhile when both switch S1 and S2 are deactivated, the AC power isrectified in Half-Bridge (HB) mode. Activating one of the 2 switchesleads to intermediate modes of rectification and selection between thesedifferent modes dynamically and in varying ratios enables the rectifier406 to counteract unsafe changes on Vrect. For example, if voltage Vrectdrops below the safe operating range, the Power Tuning Block 410activates switch S2 at a certain frequency and duty cycle to increasethe amount of power delivered to the load 408. In another example, whenVrect increases rapidly above the recommended high threshold, the PowerTuning Block 410 may deactivate both switch S1 and S2 entirely.

FIG. 4 exemplarily illustrates a schematic diagram of a wireless powersystem 400 comprising a wireless power transmitter 400 a and aself-regulating wireless power receiver 400 b. As can be noted from theexplanations disclosed, this invention is equally applicable toscenarios where multiple wireless power receivers 400 b simultaneouslyreceive power from the same wireless power transmitter 400 a. Each ofthe wireless power receivers 400 b are independently coupled to thewireless power transmitter 400 a with their own respective couplingcoefficient ‘k’. Via the disclosed self-regulation circuitry, as in theauto-tuning network 105 or the intelligent reconfigurable rectifier 406or a combination thereof, the wireless power receivers 400 b are able toregulate and control the power that they deliver to their respectiveloads 408. Their self-regulation circuitry senses the changes in theload 408 and/or the voltage Vrect and quickly counteracts the changes ifthe changes exceed a safe operating range. The self-regulation circuitryin each of the wireless power receiver 400 b controls power transfer,protects against over voltage, and provides improved load transientresponse.

The foregoing examples have been provided merely for the purpose ofexplanation and are in no way to be construed as limiting of the presentinvention disclosed herein. While the invention has been described withreference to various embodiments, it is understood that the words, whichhave been used herein, are words of description and illustration, ratherthan words of limitation. Further, although the invention has beendescribed herein with reference to particular means, materials, andembodiments, the invention is not intended to be limited to theparticulars disclosed herein; rather, the invention extends to allfunctionally equivalent structures, methods and uses, such as are withinthe scope of the appended claims. Those skilled in the art, having thebenefit of the teachings of this specification, may affect numerousmodifications thereto and changes may be made without departing from thescope and spirit of the invention in its aspects.

I claim:
 1. A wireless power system comprising: a wireless powertransmitter configured to transmit wireless power; and one or moreself-regulating wireless power receivers configured to receivewirelessly transmitted power, said one or more wireless power receiverseach including: a dynamically reconfigurable rectifier operably coupledwithin said wireless power receiver, said rectifier comprised of anintelligent switch network via which said rectifier converts saidreceived wirelessly transmitted power from alternating current (AC)power into direct current (DC) power; wherein said rectifier in saidwireless power receiver is configured to detect changes in one or bothof a load of said rectifier and an output voltage of said rectifier, andto dynamically counteract said detected changes if the changes exceed asafe operating range, said rectifier counteracts said unsafe changes bydynamically reconfiguring its mode of operation via said switch network.2. The wireless power system of claim 1, wherein said reconfigurablerectifier in said wireless power receiver comprises one or more ofpassive electronic components, active electronic components andelectronic switches.
 3. The wireless power system of claim 1, whereinpower is delivered to said load from said reconfigurable rectifier viaintermediate power regulation circuitry.
 4. A method for self regulatingwireless power system, said method comprising: providing a wirelesspower transmitter; and providing one or more self-regulating wirelesspower receivers each including a dynamically reconfigurable rectifier;configuring said one or more self-regulating wireless power receivers toreceive wirelessly transmitted power from said wireless powertransmitter and deliver a steady DC power to their respective load;configuring said reconfigurable rectifier in said wireless powerreceiver to control and regulate said received wirelessly transmitterpower and delivered power to its load by detecting changes in one orboth of a load of said rectifier and an output voltage of saidrectifier, and dynamically counteracting said detected changes if thechanges exceed a safe operating range by dynamically reconfiguring therectifier's mode of operation.
 5. The method of claim 4, wherein saidreconfigurable rectifier in said wireless power receiver comprises oneor more of passive electronic components, active electronic componentsand electronic switches.